help with role based authentication

[eluser]Abhay[/eluser]
I want to add role based authentication in a project. It is like i should be able to select each role and should have an option to set whether a particular page is to be viewed by a user of that role.
I have done three projects and all of them uses a basic authentication. It only checks if a logged in person is admin or not.
So please provide a tutorial or a layout on implementing the roles.